Heading for a record: Arctic sea ice extent tracts below 2007
The extent of the coverage of sea ice in the Arctic looks to be heading for a record low, according to new data published by the National Snow and Ice Data Center, or NSIDC. The sea-ice cover shrank in the first two weeks of August, to track below the trend for the same time period in 2007, the year in which the minimum extent, recorded in September, hit an all-time low.
The rate of ice loss has been rapid since late June and doubled in pace for a few days in early August. The especially high ice loss in early August coincided with an unusually intense regional storm, centered over the middle of the Arctic Ocean. However, it is unclear whether this storm caused the particularly rapid ice melt, NSIDC said.
On Aug. 13 the total area of Arctic sea ice was 1.97 million square miles, an area 1.04 million square miles below the average extent for the same date between 1979 and 2000 — the satellite observations that enable the day-to-day recording of the ice extent began in 1979. The extent on Aug. 13 was 180,000 square miles less than the extent on the same date in 2007, the year of the record sea-ice minimum.
There is now extensive open water on the Atlantic side of the Arctic Ocean, in the Beaufort Sea and in the East Siberian Sea, with the ice only being close to the “normal” 1979 to 2000 extent off the northeast coast of Greenland, NSIDC said. However, ice near the coast of eastern Siberia is blocking the Northeast Sea Route, while the western entrance of the Northwest Passage via the McClure Strait is also blocked.
Ice thickness The thickness of the sea ice, in addition to the area of the ice sheet, is an important parameter in assessing sea-ice conditions. Thick ice, in addition to boosting the total volume of ice, tends to be indicative of multi-year ice, ice that tends to persist for relatively long periods of time. Thin, young ice tends to melt relatively rapidly when the weather warms.
According to an article on the EurActiv.com website preliminary results from the European Space Agency’s CryoSat-2 satellite, a new satellite that uses a radar altimeter to measure the Arctic sea-ice thickness, the sea ice is disappearing at a 50 percent higher rate than previously thought. Scientists have cautioned about the preliminary nature of the results but, based on those results, they estimate that the total volume of summer sea ice is dropping at the rate of about 900 cubic kilometers per year, a rate that could result in the disappearance of all summer sea ice in the Arctic in about a decade, the EurActiv.com website says.
One problem with the loss of sea ice is what is termed a “positive feedback” effect. Essentially, ice tends to reflect solar energy back into space: With less ice on the ocean surface, less energy is reflected and more energy is absorbed by the ocean, thus accelerating the warming effect and causing yet more ice to melt.
—Alan Bailey
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